Shield Or with base wavy of Azure and Argent, a wall Vert, flanked by two embattled towers of the same, all masoned Or with windows Or, in chief the cross Gules of the Order of Santiago. Mural crown Argent with three visible towers (village rank) and white scroll with inscription in black capitals "ALCÁCER DO SAL - SANTA MARIA DO CASTELO".
Source: this webpageKlaus-Michael Schneider, 20 Jan 2017

Presentation of Santa Maria do Castelo

Santa Maria do Castelo Commune was one of the pre-2013 communes of Caminha Municipality; it had 4048 inhabitants in 2011 and covered 435.3 km². Alcácer do Sal (Santa Maria do Castelo e Santiago) e Santa Susana United Commune is the Portuguese commune, having the largest area of all. It was created in 2013, when the former urban communes of Santa Maria do Castelo and Santiago merged with Santa Susana.
Klaus-Michael Schneider, 20 Jan 2017

Shield Or, a cross Gules of the Order of Santiago, surrounded by two rice ears Vert, tied in base and crossed per saltire. Mural crown Argent with three visible towers (village rank) and white scroll with inscription in black capitals "ALCÁCER DO SAL - SANTIAGO"
Source: this webpageKlaus-Michael Schneider, 20 Jan 2017